The present invention relates to methods to suppress the nitrification of ammonium nitrogen in plant growth media and compositions which conserve soil nitrogen.
Nitrogen is essential in the growth and development of plants. A major portion of the nitrogen requirements of plants is obtained from the soil, generally in the form of ammonium ions and nitrate ions. Therefore, in order to ensure proper growth of plants by providing essential nitrogen to said plants, it is essential in crop cultivation to provide the nitrogen requirements in either the ammonium ion or nitrate ion form. Generally, bacterial conversion of organic nitrogen originating from animal manure, crop residues, fish products or the like, or provided by the distribution throughout the soil or plant growth media of an inorganic nitrogen fertilizer such as anhydrous ammonia, aqueous ammonia, urea, ammonium chloride, biuret, ammonium phosphate, cyanamide, dicyandiamide, ammonium nitrate, ammonium salts of organic and inorganic acids and nitrogen phosphorous inorganic complexes fulfills this need.
However, ammonium ions are cationic and tend to bind to the soil colloidally, thereby allowing ready leaching from said soil. Even by oxidizing or nitrificating the ammonium nitrogen in soil, this ammonium nitrogen is converted from the ammonium to nitrate form, which is very water soluble and again easily leached from the soil. It is, therefore, important for proper soil management by the farmer to control the rate of conversion of ammonium nitrogen to nitrate nitrogen in the soil.
While it is recognized that soil type, moisture content, aeration, temperature and pH all contribute to the rate of nitrification of ammonium nitrogen, temperature and pH are the primary factors governing nitrification of ammonium nitrogen in soil as evidenced by the fact that at temperatures above about 10.degree. C. and pH5, nitrification of ammonium nitrogen is very rapid and can account for production of more than 22 kg/hectare/week of nitrate nitrogen. Moreover, as the temperature rises, the rate of conversion of ammonium nitrogen to nitrate nitrogen also rises, as evidenced by the fact that at soil temperatures in the vicinity of 30.degree. C., ammonium nitrogen can be converted to nitrate nitrogen at the rate of 450 kg/hectare/week. Thus, increasing temperature may cause subsequent leaching of the soil in which substantial nitrification has occured, thereby leaving the soil essentially depleated of the nitrogen required for proper plant nutrition.
Methods to inhibit such soil nitrification relate to controlling these parameters and most often, utilizing an effective nitrification inhibitor. One such inhibitor is nitropyrin. The present invention provides other means for inhibiting this unwanted nitrification, as effective and often superior to the preferred method of using nitropyrin.
It is an object of the present invention, therefore, to provide a method for inhibiting or suppressing nitrification of ammonium nitrogen in plant growth media and soil.
It also is an object of the present invention to provide a reduced nitrogen fertilizer composition, either in liquid or solid form, containing an effective amount of a nitrification inhibitor.
It is a further object of this invention to provide a method for inhibiting the bacterial action of organisms responsible for nitrification of ammonium nitrogen in the soil such as the bacteria Nitrosomonas spp. found in the soil.
To these ends, the present invention provides both method and compositions which fulfill the objectives mentioned above.